for the DESMAN Associates

Transcription

CONDITION SURVEY REPORT
& REPAIR RECOMMENDATIONS
for the
PHOENIX PLAZA & PARKING GARAGE
Pontiac, MI
Prepared for:
City of Pontiac
Pontiac, MI
Submitted by:
DESMAN Associates
May 2012
Condition Survey Report and
Repair Recommendations
for the
Pontiac, MI
May 2012
TABLE OF CONTENTS
1. INTRODUCTION
2. EXECUTIVE SUMMARY
3. DESCRIPTION OF FACILITY
4. FINDINGS AND RECOMMENDATIONS
5. REPAIR PROGRAM AND COST ESTIMATE
6. APPENDIX A – TYPICAL FLOOR PLAN
7. APPENDIX B – CONCRETE DETERIORATION OVERVIEW
DESMAN
ASSOCIATES
1. INTRODUCTION
1.1 Authorization
DESMAN Associates (“DESMAN”) has been retained by the City of Pontiac, MI, (“The
City”) to provide a condition survey of the Phoenix Plaza & Parking Garage in Pontiac,
MI. DESMAN’s survey and scope of services was performed in accordance with the
Professional Services Contract between The City and DESMAN dated March 23, 2012.
1.2 Scope of Services
The scope of services is detailed in the above mentioned Professional Services Contract.
In summary, the scope of services is as follows:
Visually inspect the general composition and condition of the structurally
supported slabs, slab soffits, slab-on-grade, beams, columns, walls, façade, and
stair towers, in the parking structure. Note that canopy and canopy support
structure located on the plaza were excluded from our scope of services.
Visually review the condition of the existing utilities (i.e. lighting, drainage, etc.)
Perform a limited sounding evaluation of the structurally supported floor slabs to
determine the amount of delaminations in the concrete floor slab.
Perform limited sounding of slab soffits, beams, columns, walls, etc.
Investigate the configuration and degree of deterioration of the existing structural
components.
Develop a prioritized list of cost-effective repair options.
Preparation of this report documenting the results of the field survey along with
analysis of observations and recommendations for further course of action.
City of Pontiac, MI
Phoenix Plaza & Parking Garage
Condition Survey Report
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ASSOCIATES
1.3 Objective
The objective of the survey, as performed by DESMAN Associates, is to evaluate the
present condition of the facility and its overall structural integrity and develop repair
options along with cost estimates. From this study, recommendations will be made as to
the approximate extent of repair, repair materials/techniques, and their associated costs.
While the condition survey was performed with care by experienced persons, DESMAN
makes no warranty that all defects or existing conditions were discovered. The purpose of
the information presented here is to report on the present condition of the parking garage
and is not to be used for construction. Preparation of engineering/construction documents
to implement the recommended structural repairs and improvements is not part of this
task.
1.4 Definitions
Unless noted otherwise, condition appraisals are based in part upon visual observations
made at the time of the condition survey. The following terms shall apply in the
evaluation of the facility's components:
Very Good
Component is in a "like new" state, and is performing its function
as intended.
Good
Component exhibits little deterioration, and is performing its
function as intended.
Fair
Component exhibits minor deterioration, and is performing its
function as intended, but the component's rate of deterioration has
begun to accelerate.
Poor
Component has significantly deteriorated and/or is no longer
functioning as intended.
Obsolete
Component has completely deteriorated, and its state represents a
potential hazard to the overall condition of the facility.
City of Pontiac, MI
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2. EXECUTIVE SUMMARY
The structural elements of the garage displayed deterioration throughout the facility. We
observed concrete cracking, delaminations, and spalling at various locations throughout
the garage.
The concrete deterioration was predominantly seen on the structurally
supported slabs and columns, with minor deterioration observed to the concrete beams,
walls, and stair towers. A majority of the slab deterioration occurred around columns and
at column strips. At these locations, reinforcing steel is nearest to the top surface making
it more likely that chlorides reach the reinforcing steel.
The primary structural system of this facility consists of un-bonded post-tensioned castin-place concrete. At a number of locations broken and/or de-tensioned post-tensioned
cables were observed associated with the structurally supported floor slabs. The posttensioned cables are typically stressed between 25,000 lbs to 30,000 lbs and, as a result,
when they de-tension a significant amount of force is released. Due to the amount of
force that is released, sections of the de-tensioned cable can protrude from the slab and/or
the anchor assemblies become horizontally displaced – the displacement can range from
several inches to a few hundred feet. A significant amount of damage can occur, both to
property and individual, when a post-tensioned cable is de-tensioned due to the large
amount of force that is released - this is particularly true when it is unexpected or not
performed when utilizing controlled methods.
A thin elastomeric traffic bearing waterproofing membrane exists on all structurally
supported levels of the garage.
A moderate amount of wear was observed to the
membrane on the south half of the garage, with little to no wear observed to the
membrane on the north half of the garage.
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The expansion joint seals throughout the garage displayed signs of deterioration. The
deterioration consisted of missing joint seals, splits in the seals, and/or leaking through
the joint seal.
The top surface of the structurally supported slab of the Plaza was not directly viewed
during this survey due to the overburden. However, the underside of the structurally
supported slab was observed and, as a result, areas of concrete deterioration were
identified. The deterioration was primarily in the form of concrete cracking,
delaminations, and spalling.
The existing deterioration observed in the structural elements will only accelerate the
corrosion of the embedded reinforcing steel, which may result in additional structural
problems in the future. A repair program needs to be instituted to maintain the structural
integrity of the facility, provide a parking facility that can safely be used without the
possibility of falling concrete, isolated deck failures, tripping hazards, water leaking, etc.,
and develop a repair program so as to optimize the life expectancy of the products
utilized in the repairs and extend the useful life of the garage. The recommended repair
program would include performing full and partial depth concrete repairs to the
structurally supported slabs; performing partial depth repairs to the columns and beams;
performing repairs to the walls; the application of a top coat to the existing waterproofing
membrane; expansion joint repairs; etc.
Repairs to the broken/de-tensioned post-
tensioning cables will be performed to those that are discovered during the
implementation of concrete repairs.
City of Pontiac, MI
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Currently only a small percentage of the garage is being utilized and the Plaza has only
been utilized on a very limited basis in the recent past. In order for the full extent of this
facility to be safely utilized by the public, all of the “Short Term Priority Repairs” as
identified in Section 4 of this report, should be addressed. Also, it is strongly
recommended that prior to utilizing this facility to its full extent items not directly part of
our scope will need to be reviewed, addressed, or need to be operational, which include,
but may not be limited to, the elevators, revenue control system, security system, fire
alarm & suppression system, lighting (both non-emergency and emergency), signage
(both vehicular and pedestrian), and structural steel framing for canopy.
City of Pontiac, MI
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ASSOCIATES
3. DESCRIPTION OF FACILITY
The Phoenix Plaza & Parking Garage consists of an open parking structure that essentially
occupies several city blocks in downtown
Pontiac, MI. The parking garage is
partially bounded by Water Street to the
North, Woodward Avenue (south bound)
to the West, Judson Street to the South,
and Woodward Avenue (north bound) to
the East.
Orchard Lake Road/Auburn
Avenue bisects the garage in the east-west
direction. Photo #3.01 was taken near the
Photo #3.01
intersection of Woodward Avenue (south
bound) and Orchard Lake Road/Auburn Avenue and is considered a west elevation. A
finished plaza is situated on the roof level and consumes the entire footprint of the garage.
The structure consists of three structurally supported levels and one slab-on-grade level. As
mentioned, the upper most structurally supported level consists of a finished Plaza. The
remaining levels are primarily utilized for parking. The Plaza primarily consists of precast
concrete pavers, concrete planter boxes, and an amphitheater that is covered by a synthetic
fabric canopy supported by a structural
steel frame and cable system – see Photo
#3.02. The Plaza is accessed by six sets of
stairs located around the perimeter of the
structure.
Access to the Plaza is also
provided from the three multi-story
buildings adjacent to the structure. Access
within the footprint of the Plaza is
provided by stair & elevator towers, which
Photo #3.02
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also service the garage. At the time of our survey the only means of accessing the Plaza was
from the external stairs located at the north end of the garage near the corner of Water Street
and Saginaw Street – at all other access locations the doors and/or gates were locked.
The parking garage currently provides parking for the residential high rise building located to
the east of the structure, for the two office towers located to the south and west of the
structure, for events held on the Plaza,
and
public
parking
for
downtown
businesses. The layout of the facility
consists of four flat levels. The parking
levels are connected to one another by a
series of internal ramps; one set of
ramps are located in the north half and
one set of ramps are located in the south
half.
As mentioned, the Plaza Level
Photo #3.03
can be accessed from locations within
the garage as well as external stair towers. A portion of Level 3 of the garage and the
Plaza Level extend over Orchard Lake Road/Auburn Avenue. A Pedestrian Bridge extends
over Orchard Lake Road/Auburn Avenue on Level 3 connecting the south half and north half
of the garage to one another. The garage has a total of 6 stair towers and four elevator towers
– two of the elevator towers are located adjacent to stair towers. The garage has four
vehicular entrances/exits located around the perimeter of the garage – Photo #3.03 is the
entrance/exit location on the north side of the garage. Additional entrances/exits are also
located along Orchard Lake Road/Auburn Avenue. At the time of our survey a majority of
the entrance/exit locations were closed – the entrance/exit areas on the north and south sides
of the garage were open and primarily being utilized by the patrons.
The structurally supported floors consist of a two-way, cast-in-place, un-bonded posttensioned concrete slab with drop panels at the columns. The slabs are supported by
conventionally reinforced concrete columns. At limited locations, primarily at expansion
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joints, the slab is supported by cast-in-place, un-bonded post-tensioned concrete beams.
The façade consists of precast concrete. The slab-on-grade surface is a bituminous
asphalt. See Appendix A of this report for a typical floor plan of the garage.
Based on the available information, conversations with The City, and DESMAN’s walkthru of the garage, repairs and maintenance have been performed in the past but not
within the last four to five years The Plaza was renovated approximately 10 to 12 years
ago, which included repairs to the structural slab, waterproofing, miscellaneous repairs,
and new pavers.
Also, evidence of repairs throughout the garage are visible and
primarily consist of concrete floor slab repairs and the installation of a thin traffic bearing
waterproofing membrane. Based on our observations and the available information, it is
estimated that the traffic bearing waterproofing membrane was installed approximately
10 to 12 years ago.
City of Pontiac, MI
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ASSOCIATES
The following table is a list of general information regarding this facility:
GENERAL INFORMATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Total Area of Garage
Total Area of Plaza
Footprint of Structure
Typical Floor Plate Size
Typical Bay Size
Maximum Dimensions
Architectural Shape
Age Of Garage
Year Built
Number of Levels
Total Number of Spaces In Garage
Parking On-Grade
Retail Space Within Garage
Basement Parking
Construction Type
Floor Thickness Parking Garage
Floor Thickness Plaza
Floor-to-Floor Height
Lighting Type
Helix Ramp
Overall Condition of Garage
DESMAN Estimate of Repairs
Budget Recommendations
City of Pontiac, MI
874,000 s.f. +/292,000 s.f. +/672’-0” x 680’-0” +/672’-0” x 680’-0” +/34’-0” (N-S) x 32’-0” (E-W)
672’-0” x 680’-0” +/Irregular
32 years
1980
3 structurally supported and 1 slab-on-grade
2,500 ±
Yes
No
NA
Post-tensioned cast-in-place
9”
14”
10’-0”
Primarily High Pressure Sodium; Some LED & Fluor.
No
Fair
See Section 5
See Section 5
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4. FINDINGS AND RECOMMENDATIONS
For a summary of factors that influence the deterioration of concrete please refer to
Appendix B.
4.1 Observations
As outlined in the proposal, a visual examination was made of various components of the
Phoenix Plaza & Parking Garage. Deteriorated locations were quantified and recorded for
the visible elements. Photographs were also used to document the deteriorated conditions
and distressed areas observed in the facility.
A limited sounding evaluation (chain drag) was conducted on the top surface of the
structurally supported floor slabs of the parking garage to detect concrete delaminations.
DESMAN estimates that approximately 25% of the garage was chain dragged. The floor
slabs of the parking garage and the underside of the Plaza structural slab was visually
examined for concrete spalling, exposed reinforcing, cracking, and surface scaling. A
visual survey was also performed on the beams, columns, soffits, walls, stairs, and
façade. Limited sounding (hand held hammer) was also utilized on the beams, columns,
soffits, walls, stairs, and façade to aid in identification and quantification of concrete
deterioration.
During the survey, the following items were identified as areas of structural and nonstructural deterioration.
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Floor Slabs
Floor slab deterioration was identified during both the visual survey and our sounding
evaluation. The top surface of the Plaza was
not observed due to the overburden.
A
majority of the top surface deterioration
occurred around columns and at column
strips and a majority of the bottom surface
(soffit) deterioration occurred near the midspan of the middle strip – see Figure #4.01
for the location of a column strip and middle
strip in a two-way flat slab system.
Figure #4.01
The
location of the deterioration is primarily due
to the mild reinforcing steel of the floor slab being located close to the top surface in
these areas, which is more susceptible to corrosion due to chloride exposure. Concrete is
a very hard but brittle material that is very strong in compression but relatively weak in
tension. Steel is a ductile material that is strong in tension. Therefore, steel reinforcing
bars are placed in concrete structures at expected locations of high tension. In two-way
floor slabs, those areas tend to be near the top surface of the slab along column strips and
near the bottom surface, or soffit of the slab at mid-span of the middle strips.
The floor slab deterioration primarily
consisted of delaminations and spalling,
which is believed to be due corrosion of
the mild reinforcing steel as a result of
chloride
exposure.
Photo
#4.01
displays typical top surface floor slab
deterioration in the form of concrete
delaminations – note the heaving in the
top surface of the concrete slab near the
Photo #4.01
column. Photo #4.02 displays typical
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soffit floor slab deterioration in the form of concrete spalling – note the corroded
reinforcing steel at the location of the spall. In order for corrosion of the reinforcing to
occur the chloride levels within the slab
at the level of the mild reinforcing steel
must be at or above the threshold limit
to initiate corrosion. The chloride levels
to initiate corrosion are either obtained
by chloride migration through the slab
or by chloride migration through cracks,
with the former being most likely the
Photo #4.02
case in top bar corrosion and the later
being the case in bottom bar corrosion.
As mentioned, in a post-tensioned structure such as this, mild reinforcing bars, or rebar,
are placed to supplement the post-tensioning system. The reinforcing bars being placed
close to the top surface at column strips, which provides less concrete protection for the
bars, usually about 1 ½”. The concrete protects against water and chlorides from de-icing
salts from penetrating to the depth of the reinforcing steel. Even though, concrete is
somewhat porous and will allow water and chlorides to penetrate it to some degree, the
more concrete provided as protection the better.
Once exposed to water and chlorides, corrosion of steel is imminent. When steel
corrodes, it expands to several times its original size, pushing outward on its
surroundings. In the case of reinforcing steel embedded in concrete, the concrete is
“pushed” by the corrosion process inducing tensile stress within the concrete. The
concrete, being relatively weak in tension, is unable to resist this force and breaks loose
from the surrounding concrete and creating a delamination. Eventually the delaminated
concrete will completely dislodge from the surrounding concrete and become a spall.
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The post tensioning system may also be affected by the deterioration of the concrete. The
main reinforcing system consists of high strength post-tensioning cables running both
ways in a two-way slab and spaced at approximately every two-to-two and half foot
centers. Additionally, banded, or bundled, post-tensioning cables are utilized at column
strips to create beam-like conditions.
The main post-tensioning cables are placed near the top surface of the slab over column
strips and allowed to drape near the bottom surface of the slab at the middle strips. The
cables are encased in a protective plastic
sheathing in part to protect them against
corrosion. The plastic sheathing can be
breached by exposure to traffic or
pinched
by
concrete
delaminations
adjacent to the cables. The steel cables
would then be exposed to the corrosive
elements that affect the mild reinforcing
Photo #4.03
steel
with
consequences.
more
The
immediate
post-tensioning
system is the main reinforcing system in the slabs and any loss would result in
diminished structural integrity of the slab. During the survey a number of broken and/or
de-tensioned post-tensioned cables were observed – see Photo #4.03.
The post-tensioned cables are typically stressed between 25,000 lbs to 30,000 lbs and, as
a result, when they de-tension a significant amount of force is released. Due to the
amount of force that is released, sections of the de-tensioned cable can protrude from the
slab (see Photo #4.03) and/or the anchor assemblies become horizontally displaced – the
displacement can range from several inches to a few hundred feet.
Overall, the deterioration of the structurally supported floor slabs was widespread
throughout all of the supported levels of the garage, with a slightly higher quantity
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observed in the south half of the garage. The amount of deterioration observed on the
soffit of the Plaza slab was approximately a third of what was identified on the soffit of
the structurally supported slabs for the parking garage.
A limited amount of deterioration was identified on the slab-on-grade, or Level 1, of the
parking garage.
As mentioned, the
slab-on-grade consists of a bituminous
asphalt pavement. The most significant
observed deterioration was a large
heaved area on the south half of the
garage. Photo #4.04 displays cracks in
the asphalt due to heaving. This is most
likely due to the use of an unstable fill
material or a contaminated fill material
Photo #4.04
at this location.
Concrete Beams
During the survey limited locations were identified with a moderate amount of
deterioration in the form of delaminations and spalls. The deterioration is most likely due
to exposure to chloride-laden moisture/water. The exposure to chloride-laden moisture is
most likely the result of a failed/leaking expansion joint seal. The corrosion usually
occurs to the mild reinforcing, or rebar, embedded in the beams that supplement the PT
system rather than the actual PT strands themselves, which make up the main reinforcing
for PT beams.
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Concrete Columns/Walls
During the survey concrete deterioration in the form of concrete delaminations and
spalling were observed on both the
columns and walls. The deterioration is
believed to be due to corrosion of the
mild reinforcing steel as a result of
exposure to chloride-laden moisture. The
column
deterioration
was
primarily
located at the base, or near the drive
surface – see Photo #4.05. The concrete
at this location is in a “splash zone” and,
Photo #4.05
therefore, is exposed to higher chloride
concentrations.
A majority of the wall deterioration observed occurred to the spandrel wall sections. The
deterioration at these locations typically
occurred at the bottom of the wall
section and was in the form on concrete
cracking, delaminations, and spalling –
See Photo #4.06. The deterioration is
believed to be due to corrosion of the
mild reinforcing steel due to exposure to
chloride-laden moisture. The exposure,
Photo #4.06
particularly
for
the
spandrel
wall
sections, is most likely due to a failed
flexible cove joint sealant, which permitted chloride-laden water to leak through the joint
and expose the underlying concrete.
Expansion Joints
The garage primarily contains one type of expansion joint system, which is referred to as
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a premolded expansion joint system. However, at one particular location where the joint
seal had failed/was missing it appeared that a compression joint seal was installed in the
throat of the expansion joint. It is believed that the original joint seal was left in place and
a new (premolded joint seal) seal was installed over top of the existing seal.
Premolded expansion systems consist of a premolded urethane seal adhered in place with
a urethane nosing compound. There is usually a steel or aluminum plate below the
premolded seal to allow it to span the joint opening. At numerous locations throughout
the garage the joint seal is in a deteriorated state, which consists of missing sections,
splits, and tears in the seal – see Photo #4.07. The deterioration is most likely to due to
normal wear.
A failed expansion joint typically does not provide a water-tight seal. The American
Concrete
Institute
(ACI)
provides
designers
with
concrete
coverage
requirements for embedded reinforcing
steel based on types of exposure.
Typically, ACI requires less concrete
coverage of the embedded reinforcing
steel that is near the soffit or free edge
of an element, such as a slab, than for
reinforcing steel located near the top
Photo #4.07
surface of the slab. The more concrete
cover that is provided to the reinforcing steel the longer it will take for chlorides to
migrate to the level of the embedded reinforcing steel.
Therefore, when areas are
exposed to chlorides (due to a failed expansion joint seal) with limited concrete cover
premature deterioration can occur.
Waterproofing Membrane
The structurally supported levels of the parking garage are covered by what appears to be
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a cold applied thin elastomeric traffic bearing waterproofing membrane. Based on the
available information, the Plaza is waterproofed with a hot-applied rubber membrane.
The condition of the waterproofing membrane for the Plaza slab was not observed due to
the overburden.
However, there was no visible indication that the Plaza slab
waterproofing membrane was experiencing any significant leaking based on observations
made from the underside.
The waterproofing membrane utilized in the parking garage consists of a multi-layer
system, which consists of a primer, base coat, and wear course. The base coat provides
the waterproofing characteristics. The wear course, which typically incorporates a sand
aggregate for skid resistance, protects the underlying base coat.
The waterproofing
membrane on the south half of the garage displayed visible signs of wear, particularly in
high traffic areas and turning locations. At these locations the wear course and skid
resistance of the membrane were completely missing and the basecoat exposed to direct
vehicular traffic. The waterproofing membrane on the north half of the garage displayed
little to no wear. Under normal vehicular exposure, these types of systems typically have
a lifespan of five to ten years.
Stair Towers
The stair towers were surveyed and areas with evidence of deterioration were recorded.
The interior stairs of the parking garage
are comprised of metal pan risers with
concrete in-filled treads that is supported
by a structural steel frame. A majority
of the stair tower deterioration observed
consisted of cracking, delaminations, and
spalling of the concrete in the landings,
which can be seen in Photo #4.08.
Cracked CMU block, which is utilized in
Photo #4.08
City of Pontiac, MI
the construction of the walls for these
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stair towers, was also observed.
The open stair towers located adjacent to the bisecting road are also comprised on metal
pan risers with concrete in-filled treads that is supported by a structural steel frame.
Deterioration in these stairs was also observed and it was primarily in the form on
spalled/delaminated treads and failure associated with the paint system that covers the
metal pan stairs.
The stair towers around the perimeter of the structure that provide access to the Plaza
consist of conventionally reinforced cast-in-place concrete. Deterioration was observed
on these stairs, which was primarily in the form of concrete delaminations and spalling.
Facade
A visual inspection of the façade was performed from the street level and from strategic
locations within the garage.
Pedestrian Bridge
A visual inspection of the Pedestrian Bridge was performed from within the pedestrian
bridge, from street level, and from
strategic locations within the garage –
see Photo #4.09. At several locations
the wall panels were missing/damaged
and the lighting was very poor.
Photo #4.09
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Plaza
The top surface of the Plaza was visually observed, with the exception of the structural
steel frame and canopy assembly – see
Photo #4.10. The pavers, which appear
to consist of concrete, displayed little to
no deterioration. The walls/curbs that
comprise the landscaped areas all
appeared
condition.
to
be
in
“Very Good”
Two sections of the plaza
are covered by what appears to be an
elastomeric
Photo #4.10
traffic
bearing
waterproofing membrane – similar to
the garage. The membrane is displaying some wear. The top surface of the structural
slab was not observed due to the overburden. The flower beds and landscaped areas were
overgrown and not in a maintained state.
Drainage System
At numerous locations the drains appeared to be clogged, the grating missing/broken or it
was highly corroded, and/or the drain body corroded.
The branch piping, which
primarily consisted of cast iron pipe, was
cracked
at
numerous
locations
throughout the garage. Cracked pipes
usually occur when the pipe becomes
clogged, water then fills the pipe, freezes
and expands, which causes the pipe to
crack – see Photo #4.11. Portions of the
branch piping appear to be heat traced
but it is not certain whether or not this
Photo #4.11
system is currently operational.
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Lighting
The lighting for the parking garage primarily consists of high pressure sodium light
fixtures. At numerous locations the
light
fixture
is
either
missing
completely, not functioning, and/or
missing a lens.
Also, at several
locations the conduit is corroded due to
exposure to chloride-laden moisture
that migrated from above through a
crack, failed joint seal, etc. Photo #4.12
displays a section of highly corroded
Photo #4.12
conduit.
Elevators
Our scope of services did not include an assessment of the elevators. However, during
our site visit it was noticed that none of the elevators were operational. It is not known
that whether this was due to mechanical/electrical problems or that there was no current
need and the elevators were shut-down.
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4.2 Recommendations
The following section is the repair recommendations, listed in order of priority. The
specific repairs, and a time period in which the repairs should take place will be described
within each section.
It must be noted that items listed within each of Priority Repair categories primarily
address structural and durability items. At this time only a small percentage of the garage
is being utilized and the Plaza has only been utilized on a very limited basis in the recent
past. In order for the extent of this facility to be safely utilized by the public, it is
strongly recommended that items not directly part of our scope will need to be reviewed,
addressed, or need to be operational, which include, but may not be limited to, the
elevators, revenue control system, security system, fire alarm & suppression system,
lighting (both non-emergency and emergency), signage (both vehicular and pedestrian),
and structural steel framing for canopy.
Short Term Priority Repairs (Repairs within eighteen months)
The repairs considered “Short Term” should be implemented to address current structural
deficiencies and maintenance items. These repairs should be performed prior to the full
extent of this facility being utilized by the public. The “Short Term” repairs will prevent
a more costly future repair program, maintain the structural integrity of the facility, and
extend the useful life of the facility.
Structurally Supported Floor Slabs
The concrete deterioration in the form of delamination and spalling on the top surface of
the floor slabs needs to be repaired. The repairs would involve removing the deteriorated
concrete, cleaning the steel reinforcement, and patching the areas with a ready-mix
concrete material. The concrete spalls located on the soffit of the floor slabs should be
repaired in the same manner, except that a pre-packaged engineered repair material
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would be utilized. During this time all broken post-tensioning tendons would need to be
spliced or replaced and re-stressed. This would involve removing concrete from around
the PT strands and/or anchors, splicing new strand to the old strands, installing new
hardware as required, re-stressing the strands, and patching the areas with a ready-mix
concrete material.
Concrete Beams
The concrete deterioration in the form of delamination and spalling of the concrete beams
needs to be repaired. The repairs would involve removing the deteriorated concrete,
cleaning the steel reinforcement, and patching the areas with a pre-packaged engineered
repair material.
The concrete deterioration in the form of delamination and spalling of the concrete
columns and walls needs to be repaired.
The repairs would involve removing the
deteriorated concrete, cleaning the steel reinforcement, and patching the areas with a prepackaged engineered repair material.
Stair Towers
The deterioration in the stair towers will require repair. The concrete deterioration in the
landing and treads will need to be removed and replaced with either a ready mix concrete
or a pre-packaged repair material. The cracks in the landings would be repaired by
routing the existing cracks and then installing a polyurethane sealant.
The
cracked/broken CMU units should be removed and replaced in-kind.
Drainage
The deterioration associated with the drains and branch piping will be addressed. Repairs
would consist of installation of new drains, drain grating, and removal and replacement
of cracked branch piping in-kind.
City of Pontiac, MI
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DESMAN
ASSOCIATES
Lighting
The deterioration associated with the lighting and electrical conduit should be addressed.
All broken and non-functioning light fixtures would be removed and replaced in-kind and
sections of corroded conduit would be replaced in-kind. The intent upon completion of
this program would be to have all light fixtures operational.
Intermediate Term Priority Repairs (Repairs within two to five years)
These repairs will extend the useful life of the facility and minimize future maintenance
costs. These types of repairs are considered preventative in nature and primarily consist
of surface treatments and/or waterproofing membranes. Also, anticipated structural
repairs are included in this period.
It is anticipated that floor slab deterioration will continue within the facility over this
period. Therefore, we estimate that a minimum amount of slab repairs will be required in
years two thru five, both on the floor and soffit. The repairs that will be performed will
be similar to those listed in the “Short Term Repair” section of this report.
Similar to the “Structurally Supported Floor Slab” of this section, we estimate that a
minimum amount of column and wall repairs will be required in years two thru five. The
repairs that will be performed will be similar to those listed in the “Short Term Repair”
section of this report.
Concrete Beams
minimum amount of beam repairs will be required in years two thru five. The repairs
that will be performed will be similar to those listed in the “Short Term Repair” section
of this report.
City of Pontiac, MI
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DESMAN
ASSOCIATES
Stair Towers
minimum amount of stair tower repairs will be required in years two thru five. The
Traffic Bearing Waterproofing Membrane
In order to reduce future maintenance and repair costs, we recommend that the existing
traffic bearing waterproofing membrane on the south half of the garage receive a new
topcoat. This is primarily recommended due to the widespread wear of the waterproofing
membrane at this location of the garage and to provide on-going protection to the
basecoat and underlying concrete slab. In addition to the application of the waterproofing
membrane topcoat, the construction joint sealants would be removed and replaced
corresponding to the area that is being topcoated.
Expansion Joints
As mentioned, the expansion joint seals are considered to be in a deteriorated state.
Therefore, we are recommending that the existing joint seals be removed at all locations
and replaced with a new thermoplastic prefabricated, elastomeric winged seal that is
secured with an elastomeric concrete header material.
Drainage
Based on the age of these components continued deterioration is expected. The proper
removal of water is critical in minimizing future structural repairs and the long-term
durability of the structure. Therefore, it is recommended that a majority of the drains and
branch piping be replaced in-kind during this period.
City of Pontiac, MI
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DESMAN
ASSOCIATES
Long Term Priority Repairs (Repairs within five to ten years)
These repairs will extend the useful life of the facility and minimize future maintenance
costs. These types of repairs are considered preventative in nature and primarily consist
of surface treatments and/or waterproofing membranes. Also, anticipated structural
repairs are included in this period.
Again, it is anticipated that floor slab deterioration will continue within the facility over
this period. Therefore, we estimate that a minimum amount of slab repairs will be
required in years five thru ten, both on the floor and soffit. The repairs that will be
performed will be similar to those listed in the “Short Term Repair” section of this report.
minimum amount of column and wall repairs will be required in years five thru ten. The
Concrete Beams
minimum amount of beam repairs will be required in years five thru ten. The repairs that
will be performed will be similar to those listed in the “Short Term Repair” section of this
report.
Stair Towers
minimum amount of stair tower repairs will be required in years five thru ten. The
City of Pontiac, MI
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DESMAN
ASSOCIATES
Traffic Bearing Waterproofing Membrane
In order to reduce future maintenance and repair costs, we recommend that the existing
traffic bearing waterproofing membrane on the north half of the garage receive a new
topcoat. Again, this is primarily recommended due to the widespread wear of the
waterproofing membrane at this location of the garage and to provide on-going protection
to the basecoat and underlying concrete slab.
In addition to the application of the
waterproofing membrane topcoat, the construction joint sealants would be removed and
replaced corresponding to the area that is being topcoated.
Lighting
At this time it is recommended that the lights be replaced with a new energy efficient
light fixture. Also, the existing conduit will be replaced in-kind at this time.
City of Pontiac, MI
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DESMAN
ASSOCIATES
Summary of Repair Recommendations
Short Term Priority Repairs (within 18 months)
Perform repairs to the structurally supported floor slabs including PT repairs.
Perform repairs to concrete beams.
Perform repairs to concrete columns and walls.
Perform repairs to the stair towers
Perform drainage repairs
Perform lighting repairs
Intermediate Term Priority Repairs (from two to five years)
Perform anticipated repairs to the structurally supported floor slabs.
Perform anticipated repairs to concrete columns and walls.
Perform anticipated repairs to concrete beams.
Perform anticipated repairs to the stair towers
Apply a topcoat to the existing waterproofing membrane on the south half of
the garage.
Remove and replace expansion joint seals throughout
Replace a majority of the drainage system
Long Term Priority Repairs (from five to ten years)
Perform anticipated repairs to the structurally supported floor slabs.
Perform anticipated repairs to concrete columns and walls.
Perform anticipated repairs to concrete beams.
Perform anticipated repairs to the stair towers
Apply a topcoat to the existing waterproofing membrane on the north half of
the garage.
Replace lighting system.
City of Pontiac, MI
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DESMAN
ASSOCIATES
5. REPAIR PROGRAM AND COST ESTIMATE
5.1 Repair Program
Prior to implementing repairs, it is recommended that any loose or broken concrete be
removed from the deteriorated areas. The proposed repair programs are intended to
eliminate public safety hazards by repairing the structural deterioration, and extending the
useful life of the facility.
In order to ensure the longevity of the repairs, a basic repair approach has been developed
for implementing repairs throughout the ramp. The repair programs are recommended for
all areas of deterioration identified during the survey. The repair approach will include
performing all the structural and non-structural repairs to the ramp. The initial step of the
repair program is addressing the Short Term Priority Repairs.
5.2 Phasing
It is recommended that all structural and non-structural repairs should be performed
under one repair program. Repairs will need to be phased in order to maintain traffic flow
and meet required available parking requirements. During the implementation of the
repairs traffic flow will need to be maintained and access to each level must be provided.
5.3 Cost Estimates
Due to the preliminary nature of this study, the following estimates are presented for
budget purposes only and are not guaranteed construction costs. Formal bids should be
obtained from qualified contractors. The estimate is based on DESMAN’s experience
with similar parking garage rehabilitation projects and prices for similar repairs and
preventive maintenance work in the Greater Detroit area. The estimates exclude
engineering costs associated with the development of construction documents and
construction administrative/management services.
City of Pontiac, MI
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DESMAN
ASSOCIATES
Construction Cost Estimate
Pontiac, MI
May 2012
Item
1
2
3
4
5
6
7
8
9
10
11
Description
General Conditions
Floor Repairs
PT System Repairs
Vertical Repairs
Overhead Repairs
Masonry Repairs
Expansion Joint Repairs
Waterproofing
Striping
Drainage Repairs
Lighting Repairs
Subtotal
15% Contingency
Total
Short Term Repairs
(within 18 months)
Intermediate Term Repairs
(within 2 to 5 years)
$150,000
$417,000
$282,000
$242,000
$275,000
$30,000
$0
$0
$0
$40,000
$131,000
$1,567,000
$235,000
$1,802,000
Long Term Repairs
(within 5 to 10 years)
$130,000
$41,000
$28,000
$24,000
$28,000
$3,000
$299,000
$674,000
$25,000
$120,000
$0
$1,372,000
$206,000
$1,578,000
$360,000
$47,000
$32,000
$28,000
$31,000
$4,000
$0
$783,000
$29,000
$0
$2,600,000
$3,914,000
$587,000
$4,501,000
Notes:
1. The figures are exclusive of annual budgets for operational issues such as light bulb
replacement, janitorial services, equipment maintenance contracts, etc.
2. Costs are expressed in 2012 dollars. Inflation and escalation have not been included
in the cost estimates.
3. A premium cost of 10% to 15% over estimated costs is possible if a single work item
is divided over multiple years due to budget constraints.
4. Figures are exclusive of any abatement of hazardous materials or revenue control
system changes.
5. Engineering and other 'soft' costs are not included in the above and are typically 5-8%
of the noted construction costs.
City of Pontiac, MI
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DESMAN
ASSOCIATES
Redevelopment Options
In-lieu of performing the recommending repairs, as identified above, the parking
structure could be demolished and the land utilized for another use. At this time the cost
associated with demolishing this facility is unknown.
This concludes our condition assessment report related to this facility. A formal meeting
should be scheduled between the Owner and Engineer to discuss our findings and
recommendations. In the meantime, if you should have any questions please do not
hesitate to contact us.
Respectfully submitted,
DESMAN Associates,
A Division of Desman, Inc.
Matthew W. Repasky, P.E.
Senior Associate
City of Pontiac, MI
Page 30
Appendix A
Typical Floor Plan
Appendix B
Concrete Deterioration Overview
Parking Ramp Deterioration and Restoration Overview
Concrete is a stone-like material created by placing a carefully proportioned mixture of cement,
sand, gravel or other aggregate, and water into forms shaped to the dimensions of the desired
structure and allowing it to harden. Concrete has existed and been used in various ways for
thousands of years, and is currently used as a building material worldwide. The advantages of
this building material include its high fire and weather resistance, local availability at low costs,
and high compressive strength. However, it is a relatively brittle material whose tensile strength
is low compared to its compressive strength. Beginning in the late 19th century, and continuing
throughout the 20th century, steel bars have been used to reinforce concrete members where the
low tensile strength would otherwise limit load-carrying capacity. Under normal environmental
conditions, steel reinforcing bars embedded in concrete do not corrode. A protective film of iron
oxide forms on the surface of the steel when it is encased in concrete. The natural alkalinity (pH
value of approximately 13.2 or higher) associated with hydration of the Portland cement in the
concrete is usually sufficient to keep this protective film stable.
However, the service environment of parking structures is more similar to that of highway
bridges than most other buildings. Often these structures are exposed to extreme seasonal and
daily ambient temperature variations. The associated thermal volume changes can cause cracking
of the slabs, beams, columns, and walls. Moisture and oxygen can enter the concrete through
these cracks and initiate the corrosion process. With time, the volume increase associated with
the corrosion formation will generate enough force to delaminate the concrete cover over the
reinforcing steel.
With the widespread use of salt de-icing programs for our national highways, the conditions of
our bridge decks, parking garages and other reinforced concrete structures directly exposed to
these elements began to deteriorate. The relationship between the deterioration and the use of deicing salts was most evident by the extent of deterioration found in the “snow belt” states. Due to
the development of this deterioration, programs were initiated to study the cause and effect of the
problem so that repair programs and preventive maintenance procedures could be instituted.
Research during this period confirmed that corrosion of the embedded reinforcing steel is
typically the primary cause of the structural deterioration. It was further determined that the
presence of chloride ions in the concrete, from both external and internal sources, greatly
accelerates the corrosion process. External sources of chloride ions primarily consist of de-icing
salts that have been applied directly to the slabs or have been carried into the parking garage by
vehicles. Internal sources are typically provided by calcium chloride admixtures to the concrete
such as those used in winter months to speed the temperature sensitive curing of the concrete
mix. According to the American Concrete Institute, chloride ion concentration of 0.2% by weight
of cement, or chloride concentrations of approximately 1.1 lb/cy of concrete to 1.6 lb/cy of
concrete, can initiate corrosion of the embedded reinforcing steel in concrete structures.
Repair programs began to consider that the only method to stop subsequent corrosion of
reinforcing steel was one in which all concrete that contains threshold values of chloride ions
was removed, and chloride ions and moisture were prevented from entering the new concrete.
However, removal of all concrete containing significant amounts of chloride ions is seldom a
practical solution.
A normal assumption made during a condition evaluation is that the structure was adequately
designed, and was constructed in accordance with that design. Extensive destructive testing to
confirm that existing conditions meet the original design criteria is typically beyond the scope of
a condition assessment survey. As stated by the American Concrete Institute (ACI) Committee
362 in their State of the Art Report on Parking Structures, “Repairing an existing deteriorated
structure involves many unknowns, uncertainties, and risks. Especially with regard to repair of
deicer caused corrosion damage, the process is considered an extension of the useful life of the
deteriorated structure. It is not equivalent to building a new structure with current technology.”
Therefore, in the development of alternate repair programs, contingency funds must be
anticipated and included in the probable construction costs to account for concealed, unknown,
or unexpected conditions that may be encountered.
The successful extension of the service life of a structure will also depend on upon the degree of
continuing maintenance provided after a repair program is completed. Usually, some continuing
deterioration can be expected to occur, and funds should be set aside to address this condition in
future years.

for the DESMAN Associates

Transcription

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